在浓度30%的盐水中加入100克水，浓度降到20%，再加入（　　）克盐，浓度会恢复30%．

肖肖近来很烦恼，因为这段时间，老师要求班上创建一个QQ群，每天各科老师在群里发一些作业，同学们也可以在群里交流一些学习的心得，可是肖肖的妈妈非要肖肖的QQ密码，说是为了解一下她的思想动态，肖肖很不想给妈妈，但怕妈妈不高兴，只好把QQ密码给了妈妈。

先通读下面的短文，掌握其大意，然后从A、B、C、D四个选项中选择可以填入空白处的最佳答案．

    One night I saw something on the news that made me sad．It was1a group of homeless(无家可归的)people sleeping outside in the cold．

    So I decided to start a2to raise many for the homeless．I called it the Rock Club,At the beginning,there were only five members in it，3that quickly grew to about twenty．I didn't have to ask anyone if they wanted to be a4．In fact，they came up to me and asked me if they could5the club!

    We spent all of our free time on rock painting．We painted animals,flowers and even the names of sports teams on our rocks．We'd go around the school to6people who would buy them．By Christmas，we had raised thirty．three dollars and then we gave the money to a homeless shelter(收容所)in town．We all felt7that we could do something to help the homeless．

    A few days later,a newspaper reporter(记者)came to our school to8with us about our club and took a photo of us．The photo and article(文章) 9in the newspaper the next day．Later,10school,joined by three other schools，started a project for kids to help homeless shelters．

    Something as simple(简单的)as some painted rocks and a few caring kids made me know that I don't need much to make a difference．

中国人民银行下调住房贷款利率2％，并把新购住房首付款比例由30％下调至20％。这体现了政府运用        调控房地产市场。

①经济手段    ②财政政策    ③行政手段    ④货币政策

联合国已将每年的5月31日定为“世界无烟日”．下列对吸烟的认识，不正确的是（　　）